1. Field of the Invention
The present invention relates to a titanium material, a method for production thereof, and an exhaust pipe. More particularly, the present invention relates to a titanium material from which to make an exhaust pipe for two- or four-wheeled vehicles.
2. Description of the Related Art
By virtue of their higher specific strength than ordinary steels, titanium alloys are making inroads in the field of transportation, particularly automobiles requiring weight reduction. One way under study to realize weight reduction is by replacement of prevailing stainless steel exhaust pipes with titanium alloy ones. Unfortunately, exhaust pipes get hot partly above 500° C. and titanium alloys (without special treatment) are subject to rapid oxidation at such high temperatures, which poses a problem with durability.
Some ideas have been proposed to improve the oxidation resistance of titanium alloys. They include an aluminum-clad titanium alloy material (Japanese Patent Laid-open No. Hei-10-99976), a method for plating by vapor deposition with Al—Ti alloy (Japanese Patent Laid-open No. Hei-6-88208), and a method of forming a TiCrAlN film by PVD (Japanese Patent Laid-open No. Hei-9-256138). Unfortunately, cladding involves complex processes, which leads to high production cost and poor economy. In addition, vapor deposition and PVD present difficulties in forming oxidation-resistant film inside an exhaust pipe.